Polymethylated Flavonols of Chrysosplenium americanum I. Identification and Enzymatic Synthesis

Abstract

Abstract Polymethylated Flavonols, Identification, Enzymatic Synthesis, O-Methyltransferase, Chrysosplenium americanum, Saxifragaceae The major flavonoid constituents of Chrysosplenium americanum (Saxifragaceae) were identified by UV-, NMR-and mass spectroscopy and the analysis of their hydrolytic products. They consisted of two 2'-O-β-D-glucosides of partially methylated 2'-hydroxyquercetin and four 5'-O-β-D-glucosides of partially methylated 6-hydroxyquercetin (quercetagetin). The O-methyltransferase system of this tissue can catalyse the stepwise O-methylation of quercetin, but not quercetagetin, to its 3,7,4'-triOMe-dervative. It is postulated that the latter compound may serve as a branching-point intermediate in the biosynthesis of the naturally occurring O-methylated flavonols of this tissue.